Polysilicon has a higher mobility rate and stability than amorphous silicon. Low temperature polycrystalline silicon (LTPS) thin film transistors have found a wide range of applications in display field. In conventional LTPS thin film transistors, the channel region is doped with a first dopant of a first type, and the source electrode and drain electrode contact region is doped with a second dopant of a second type. The first dopant and the second dopant are different types of dopants selected form a p-type dopant and an n-type dopant.